Hydroisomerization process



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Sept. 13, 1960 lawaai/pulg' :anual/00H um@ Qmm United States Patent "O HYDRoIsoMERIzA'noN PRo cEss Vladimir Haensel, Hinsdale, lll., assignor, by mesne assgnments, to Universal Oil Products Company, Des

Plaines, lll., a corporation of Delaware Filed Feb. 27, 1958, Ser. No. 717,849

Claims. (Cl. 260-668) This invention relates to the hydroisomerization of saturated hydrocarbons in the presence of a hydroisomerization catalyst. More particularly, this invention relates to the hydroisomerization of paraliin hydrocarbons in anintegrated process comprising hydroisomerization, dehydrogenation, and recycle of hydrogen produced in the dehydrogenation step as the sole source of makeup hydrogen for the hydroisomerization step. Still more particularly, this invention relates to the vapor phase hydroisomerization of parain hydrocarbons boiling above butanes and pentanes in which process high yields of high antiknock hydrocarbon fractions are produced with minimum loss to byproducts such as dry gas and high boiling materials. Along with thek production of this high antiknock hydrocarbon fraction there is produced an aromatic hydrocarbon fraction which may be utilized per se or if so desired combined with the above mentioned high lantiknoclr hydrocarbon fraction for thel production of the maximum quantity of high antiknock hydrocarbons. Simultaneously with the maximum utilization of available relatively low octane number straight chain paran hydrocarbons, this invention relates to a particular series of process steps, the use of which results in maximum hydroisomerization catalyst life and optimum product quality. This invention is particularly .present invention as will be set forth hereinafter.

Production of highly branched chain paratlinic hydrocarbons having high antiknock properties and therefore suitable for use in automotive and aviation fuels s of considerable importance in the petroleum rening industry. Furthermore, the recent introduction of automobile engines of high compression ratios has necessitated the utilization of high antiknock fuels inthese engines to obtain maximum horsepower output therefrom. Thus, the demand for higher land higher octane number fuels has led to the need for increased quantities of highly branched chain paratin hydrocarbpns for use as blending agents in existing supplies of gasoline. A convenient source of highly branched chain parain hydrocarbons is the catalytic isomerization of less highly branched chain parain hydrocarbons. Normal butane and normal pentane have been isomer-ized to isobutane and isopentane, respectively, by various prior art processes utilizing either liquid or vapor phase. However, it is Well known in the prior art that cracking occurs along with isomerization and that this cracking increases with increasing molecular weight of the hydrocarbon re.-

2,952,716 `Patented Sept. 13, 1960 ICC iactant. There has been considerable difficulty in thev successful isomerization of hexane fractions on a commercial scale. A process for such isomerization is particularly attractive when it is realized that a hexane fraction can be converted by proper isomerization and fractionation into a pool of motor fuel blending components having an F-l-i-3 cc. octane number of over 100. It is therefore an additional object of this invention to provide a process which will result in the production of these desired high octane number hexane isomers.

Prior art processes for the isomerization of saturated hydrocarbons have taught the utilization of various catalytic agents to accelerate the desired molecular rearrangement at the conditions selected. Ordinarily, the catalytic agents utilized have comprised metal halides such as aluminum chloride, `aluminum bromide, antimony chloride, etc., which were activated by the addition of the respective hydrogen halide thereto. Furthermore, the prior -art has taught that these catalytic agents may be additionally utilized in the presence of added hydrogen. Such catalytic agents are known to be very active and eiect high conversions per pass. However, this high activity is accompanied by many disadvantages. `One of the greatest disadvantages is the fact that these catalytic materials not only accelerate isomerization reactions,but they also induce decomposition reactions. These decomposition reactions are particularly detrimental to the overall economics of an isomerization process since they cause a loss of a portion of the charging stock as Well as increasing catalyst consumption by the reaction of fragmental material with the catalytic agent to form sludge-like materials. As stated hereinabove, the prior art teaches the utilization of hydrogen along with these catalytic agents. This hydrogen has been utilized inran attempt to cause reaction of these fragmental materials which are formed by decomposition with the hydrogen thus resulting in a decrease in sludge formation. While there has been some indication that such utilization of hydrogen is beneiicial, processes utilizing the same along with the above mentioned catalytic agents have notbeen accepted as economically feasible by the petroleum industry. The process of the present invention overcomes these disadvantages by utilization of more recently developed catalysts and thus the use of this process 'along with these catalysts results in-the attainment of isomerization reactions, more specically hydroisomerization reactions, which have hereinbefore been unavailable to the petroleum industry.

As stated hereinabove, the process of the presentinvention is particularly `directed to the hydroisomerization of hydrocarbon fractions comprising hexane hydrocarbons or hydrocarbons containing six carbonvatoms. Hexane hydrocarbons boil from about 45 to about *P C. (11B-185 F.) and analyses of typical hexane fractions show that they contain varying quantities of 2,2-dimethylbutane, 2,3-dimethylbutane, Z-methylpentane, B-methylpentane, normal hexane, methylcyclopentane, and cyclohexane. Because of their respective boiling points, these hexane hydrocarbon fractions also contain varying small quantities of cyclopentanel (boiling point 120.7 F.) and dimethylpentanes (boiling points 174.6-- 176.9 F.). The trimethylbutane, 2,2,3-trimethylbutane, which boils at l77.6 F. also falls within the hexane hydrocarbon boiling range but occurs naturally in such small quantities that it is not usually found as a component of these fractions. The boiling points and octane numbers of these six carbon atom hydrocarbons are giveninthe following table: y Y

i ABLEI Boiling Point F-l Octane N o.

C. F. Clear +3 cc.

gnmirnethylpntae.. 49. 7 121.5 92.3 104.0 2,3-Dimethylbutane 58.0 136.4 103, 5 120 2-Methylpentane Y 60.*3 140. 5 73.4 93.1 B-Methylpentane- 63. 3 145. 9 74. 5 93. 4 68.7 155.7 25.0 65.3 71; 8 161. 3 92. 0 103. 1 80.1 176. 2 )120 120 Cyclohexane 80. 7 177. 3 84.0 97. 4

Y By the process of this invention the high octane number dimethylbutane componentsand cyclohexane are not passed to the hydroisomerization reactor but are fractionated from the combined feed to the process. Such dimethylbutaneY components include 2,2-dimethylbutane and 2,3-dimethylbutaue. Furthermore, the benzene and cyclohexane components of the combinedfeed are not passed to the hydroisomeriza'tion reactor but are instead passed to aV dehydrogenation reactor for the production of aromatic hydrocarbons, namely benzene, with the concurrent production of hydrogen which is utilized as the sole source of makeup hydrogen in the process. When processingphexanesV in the process of this invention, the hydroisomerization,reaction zone feed will comprise 2- methylpentane, 3-methylpentane, normal hexane, and methylcyclopentane, This hydroisomerization reaction zone feed will be converted therein to an equilibrium mixture of hexane isomers including the dimethylbutanes and cyclohexane, =In this manner a total gasoline pool having an Fl-l-S cc; octane number of greater than 100 is produced and methylcyclopentane is converted to cyclohexane thus increasing the quantity of benzene which can ultimately be produced as the second product from the process. V

One embodiment of the present invention relates to a process for theV hydroisomerization of an isomerizable saturated hydrocarbon fraction characterized by an average molecular weight greater than about 80, such hydroisomerization being carried out at hydroisomerization conditions in thevpresence of hydrogen and a hydroisomcriza- Vtion catalyst comprising a hydrogenation component deposited on an acid-acting support, which comprises Sep- Yarating dehydrogenatable cycloparans naturally occurring in the fresh feed and produced -in the hydroisomerization'process from the combined feed tov the hydroisomerization process, dehydrogenating said cycloparans in the presence of a dehydrogenation catalyst at dehydrogenation conditions to produce hydrogen and aromatic hydrocarbons, removing said aromatic hydrocarbons from the process, and recycling at least a portion of said hydrogen to the hydroisomerization process as -the sole source of `makeup hydrogen therefor. Another embodiment of the present invention relates to a combination hydroisomerizationdehydrogenation proc.- cess for the simultaneous production of dimethylbutanes and benzene, saidrprocess self-suicient in hydrogen requirement, ,which comprises passing to a rst fractionatron zone an isomerizable hexane hydrocarbon fraction m combination with liquid phase hydroisomrization z'one efuent Y produced as hereinafter described, fractronating said hydrocarbons to produce a substantially cyclohexane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottomsV fraction kcomprising cyclohexane, passing said cyclohexane jbottoms Vfraction to a dehydrogenation zone herein after described, passing said( substantially cyclohexanefree'roverhead hexane fraction from said first fractionanon zone to a second Vfractionation zone as. feed therefon-fractionating said hydrocarbons toproduce an overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes and'to produce a bottoms hydrocarbon Y fraction containing methylpent'anes, normalahcxll?,

j 'a' 2,952,713" i r fs a F, Y

wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a liquid hourly space velocity of from about 0.1 to about l0 in the presence of a` hydroisomerization `catalyst comprising a hydrogenation component deposited on an acid-acting support to an equilibriumnmixture of hexane hydrocarbons including 2,2- and 2,3-dimethylbutanes, methylpentanes, normal hexane," methylcyclopentane,V and cyclohexane, recycling the hydroisomerization zone eifluent to the first mentioned fractionation zone as aforesaid to recover Acyclohexane` therefrom and` to allow recovery therefrom of 2,2- and 2,3-dimethylbutane produced in the process in said second, fractionation zone as aforef' said and to separate methylpentanes, normal hexane, and methylcyclopentane Vas `aforesaid for reuse and internal recycle in said process, dehydrogenating said cyclohexane from the bottoms of said first fractionation zone in a dehydrogenation zone in theppresenceof a dehydrogenation catalyst at dehydrogenation conditions to hydrogen and benzene, 4removing said benzene as the second prod-- uct from the process, and recycling at least a portion of said hydrogen to 4the hydroisomerization zone as theA sole source of makeup hydrogen therefor.

A speciiic embodimentof this invention relates to a. combination hydroisomerization and dehydrogenation process for the simultaneous production of dimethylbutanes and benzene, said process self-sufficient in hydrogenrequirement, which comprises passing to a rst yfractionation Vzone an isomerizable hexane hydrocarbon fraction'in combination with liquid phase hydroisomerization zone eliiuent produced as hereinafter described, fractionating said hydrocarbonsto produce `a substantially cyclohexane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising cyclohexane, passing said cyclohexane bottoms fraction toA aV dehydrogenation zone hereinafter described, passing said substantially cyclohexane-free overhead hexane fraction from said first fractionation zone to a second fractionation zone as feed therefor, fractionating said hydrocarbons to produce an overhead hydrocarbon fraction containing 2,2- and 2,3- dimethylbutanes and ,to produce -a bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes as one product from the process, passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane,y and methylcyclopentane along with hydrogen at least some of which is produced by dehydrogenation'as hereinafter described to a hydroisomerization zone maintained ata temperature of from 300"` F. to about 500". F, and ata pressure of from about /to aboutr1000 pounds per square inch wherein methylpentanes, normal hexane,V and methylcyclopentane are isomerizedsatga liquid hourly space velocity of from about 0.1 to about. 10V in the presence ofv a hydroisomerization Y catalyst. comprising. platinum deposited on alumina impregnated .with aluminum chloride to an equilibrium mixture of hexane hydrocarbons including 2,2-and` 2,3-dimethylbutanes, in ethylpentanes,V normal hexane, methylcyclopentane, rand .cyclohexane, recycling the, hydroisomerizationqzone effluentto the first mentioned fractionationzoneas Vaforesaidto recover cyclohexane therefrom -andfto -allow -recovery. therefrom of :2122- arid 2,3-dimethylbutanes lproduced in`the process in said second fractionation zone as aforesaid and to separate methylpentanes, normal hexane, and methylcyclopentane as aforesaid for reuse and internal recycle in said process, dehydrogenating said cyclohexane from the bottoms of said first fractionation zone in a dehydrogenation zone in the presence of a dehydrogenation catalyst comprising platinum deposited on acid-free alumina at a temperature of from about 5,00" F. to about 1000 F., a pressure of from about atmospheric to about 500 pounds per square inch, and at a liquid hourly space velocity of from about 0.1 to about 100 to produce hydrogen and benzene, removing said benzene as a second product from the process, and recycling at least a portion of said hydrogen to the `hydroisomerization zone as the sole source of makup hydrogen therefor.

The combination process of this invention has several advantages, all interrelated. The process prevents the buildup of heavier products in the combined feed to the reaction zone since these heavier products are eliminated by removal in the bottoms from the first fractionation zone along with the cyclohexane. The hydroisomerization step of the process is carried out in the presence of hydrogen and more recently developed hydroisomerization catalysts comprising hydrogenation components deposited on acid-acting supports. In the presence of hydrogen and in the presence of these catalysts, sludge formation, which appears to -be a concurrent reaction with hydroisomerization is minimized, or for all practical purposes eliminated. Ihis sludge elimination is accomplished by hydrogenation of the fragmental materials leading to the sludge or by hydrogenation of the sludge prior to the accumulation thereof in quantities which cause catalyst deactivation. It has also been theorized, although not yet confirmed, that the hydrogen plays -an essential role in one of the proposed reaction steps of the mechanism by which the hydroisomerization process takes place. However, no intention is meant to be inferred therefrom that lthe particular hydroisomerization reactions which take place herein yare to be limited to any particular theory or reaction mechanism. The process of the present invention provides maximum utilization of naphthenic hydrocarbons containing six carbon atoms in the cycloparafhn ring by removal thereof prior to isomerization in the lower portion of the first fractionation zone. By elimination of the cyclohexane and derivatives thereof from the reaction zone combined feed, conversion of cycloparaflins containing iv'e carbon atoms in the cycloparaffin ring, such as methylcyclopentane, to cycloparans containing six carbon atoms in the ring is accomplished due to equilibrium factors. Benzene which is naturally occurring in many hexane hydrocarbon fractions is substantially removed along With the cyclohexane from the bottom of the rst fractionation zone. This removal, however, is not 100% due to azeotroping of the benzene with the paran hydrocarbons. However, benzene which is carried over into the hydroisomerization zone is hydrogenated therein to cyclohexane and this cyclohexane is then recovered by the particular fractionation as set forth hereinabove. By elimination of cyclohexane naturally occurring in the reaction zone feed, by `elimination of cyclohexane produced during hydroisomerization, and by reduction of the benzene content of the combined feed, hydrogen consumption in the process is minimized. This results in an economic advantage since large quantities of hydrogen do not have to be furnished to the process. Major hydrogen consumption is that due to hydrogen solubility in the reaction zone effluent in the high pressure separator, described hereinafter. Some hydrogen loss occurs, however, through the small amount of hydrocracking which inherently takes place in the process and through hydrogenation of higher molecular weight fragmental materials which tend to form sludge or by hydrogenation of sludge itself. The process prevents so-called reverse isomerization of high octane number dimethylbutauesto other hexane isomers by separation of these high octane number components prior to isomerization. At any particular isomerization reaction temperature, the formation of hexane isomers is limited by the equilibrium distribution of these isomers. By having the high octane number dimethylbutanes present in the hydroisomen'zation feed, the conversion of monomethylpentanes and normal hexane to these compounds cannot proceed to .the same extent as when these isomers are absent. Furthermore, the equilibrium among hexane isomers is dynamic so that the desired dimethylbutane isomers can undergo reverse isomerization if present in substantial quantities in the hydroisomerization feed. Another advantage of the process of the present invention is that hydroisomerization catalyst deactivation or destruction is min-imized or substantially eliminated -by distillation drying of the hydroisomerization zone feed and rejection of small quantities of water contained therein is accomplished along with the dimethylbutanes in the overhead from the second fractionation zone."

Thus, the hydroisomerization zone feed is a fractiona- .tion zone bottoms product and by this means full advantage -is taken of maximum distillation drying. All hydroisomerization catalysts depend upon an acid function to promote or to accomplish the desired reaction. This acid function is destroyed or decreased by contact with water. The preferred catalysts of the present -invention which operate at elevated temperatures contain this `acid function in quantities ranging from about-2 to about 20% by weight thereof, and are thus utilized at intermediate processing conditions. Thus, small amounts of water which can be brought in with the feed stock cause relatively rapid catalyst deactivation. Utilization of the process of the present invention prevents this deactivation. By elimination of dimethylbutanes and cyclohexane from the hydroisomerization zone feed, the quantity of total feed is reduced as well as the combined feed ratio-and thus the investment necessary for catalyst can be substantially reduced. By dehydrogenation of dehydrogenatable cycloparans, for example, cyclohexane, a second desirable product is produced in the process, namely, aromatic hydrocarbons such as benzene. Not only is this second product produced in substantial quantities but the hydrogen which is produced along with this hydrocarbon is extremely pure and is utilized as the sole source of makeup hydrogen necessary for the hydroisomerization step in the process. This combination results in ythe process being self-sufficient in hydrogen requirement and thus eliminates the necessity for an outside source of hydrogen and allows installation of the process in locations where the cost of such hydrogen would ordinarily prevent utilization of hydroisomerization for upgrading the octane number of hydrocarbon fractions. These and other advantages will be explained more fully in the following detailed description of the process of this invention.

As set forth hereinabove, Ythis invention relates to a process for the hydroisomerization of an isomerizable saturated hydrocarbon fraction characterized by an average molecular weight greater than about 80. Hydrocarbons within the scope of the above limitation and utilizable in the process of this invention include methylcyclopentane normal hexane, Z-methylpentane, 3-methylpentane, Z-methylhexane, 3methylhexane, 3-ethylpentane, normal heptane, ethylcyclopentane, normal octane', Z-methylheptane, 3-methylheptane, etc. As stated previously, the process of this invention is particularly applicable to the isomerizationV of hexane hydrocarbon fractions. These hexane hydrocarbons may be obtained from various sources including fractionation from straight run gasoline, straight run naphtha, natural gasoline, catalytically reformed naphtha, catalytically reformed gasoline, etc. Analyses of typical hexane fractions from various crude oil sources are givenV in the following Table It. l

TABLBn Bar- Penn- South Gulf Okla- Wyo- Ara- Natl Natl Composition, Vol Percent nnus sylva- Loui- Coast homa ming bian Gasol. Gasol Crude n siana Texas Texas Cyclopentane Y 2 2 3 3 4 2 2 5 2,2Dim'ethylbutaue Tr 3 2 3 1 -1 1 2 3 2,3-Dlmethylbutane-. 5 5 '5 5 Y 2 3 3 4 6 Z-Methylpentane- 27 25 25 22 22 22 28 28 3-Methylpentane- 19 18 18 20 15 14 16 17 l5 n-Hexane 32 36 31 30 40 35 44 34 23 Methylcyclopentane. 16 6 14 3 14 18 7 9 `14 Dimethylpentanes Tr Tr 1 1 1 1 Tr Tr Cyclohexane 1 Tr 1 7 1 1 2 1 2 Benzene 2 2 1 3 2 1 2 3 4 Total 100 100 100 100 100 100 100 100 100 0| Cyclles 4.-.-. 19 8 16 13 17 20 11 v13 20 Octane N0. F-l-I-3 CG 88 86 88 90 85 86 82 86 92 A detailed description of the processing of one of these hexane hydrocarbon fractions by the process of the present invention will be given hereinafter.

Various Vhydroisomerization catalysts are utilizable within the generally broad scope ofthe process of the present invention. These catalysts may be defined as comprising a hydrogenation component deposited on an acid-acting support. The acid-acting support may inherently have this property or its acid-acting characteristics may be added theretoV either before or after deposition of the hydrogenation component thereon. Suitable supports may be selected from among the dilerent refractory oxides including silica, alumina, silica-alumina, silica alumina magnesia, silica-alumina-zirconia, silicazirconia, etc. 'Ihese supports may be naturally occurring or may be prepared synthetically.` Other suitable naturally occurring refractory oxides include acid-acting clays such as Filtrol, Tonsl, etc., diatomaceous earths, montmorillonites, etc. Depending upon whether or not the refractory oxidek support is naturally occurring or prepared synthetically, and depending upon the kmethod of preparation, Vand upon the treatment of the support thereafter, these various supports will have surface areas ranging from about to about 500 square meters per gram. In some of these supports the acid-acting function is inherently present, as stated hereinabove, for example, when silica-alumina or silica-alumina-zirconia is used as the support. The eifectiveness of this acid-acting function in such a support is controlled by the quantities of the respective components, land by the treatment of the composites, particularly by calcination, prior to or after compositing the hydrogenation componenty therewith. The preferred catalysts used in the hydroisomerization 'zone in the process ofthe present invention comprise a refractory oxide, a hydrogenation component, and ya Friedel-Crafts metal halide. -In these preferred catalysts the above mentioned refractory oxides have composited therewith Ia hydrogenation component and then a metal halide of the Friedel-Crafts type. The hydrogenation component will normally be selected from groups VHB) and VIII of the periodic table or mixtures thereof. Such hydrogenation components include chromium, molybdenum, tungsten, iron, cobalt, nickel, and the sO-called platinum group metals. IBy a platinum group metal is meant a noble metal, excluding silver and gold, and selected from platinum, palladium, ruthenium, rhodium, smium, and iridium. These metals are not necessarily equivalent in activity in the catalysts utilized in the hydroisomerization step of the process of the present invention and of these metals, platinum and palladium are preferred, and particularly platinum is preferred. A Friedel-Crafts metal halide is associated with the solid composite of `refractory oxide andV hydrogenation component for Yuse as a catalyst in the process of the present invention.V Suitable Friedel-Crafts metal halides include aluminum chloride, aluminum bromide, zinc chloride,

ferrie chloride, ferrie bromide, beryllium chloride, gallium chloride, titanium tetrachloride, Yzirconium chloride, stannic chloride, etc. Of these Friedel-Crafts metal halides, the aluminum halides are preferred, and `of the aluminum halides, aluminum chloridey is particularly preferred. Furthermore, these metal halides are Vnot necessarily equivalent when'utilized in forming the catalysts described hereinabove. The preferred catalyst composition comprises alumina, platinum, and aluminum chloride. The alumina is preferably synthetically prepared gamma-alumina and is of a high degree of purity. These aluminas may include, lin `one embodiment, from about 0.01 to about 8% of`what is known in the tart as combined halogen, based on the weight of the dry alumina, the combined halogen'preferably being uorine. Furthermore, it isV generally preferred to' utilize from about 0.01 to about 2% by weight of platinum based on the dry alumina. When utilizing other hydrogenation components such as those of the so-called iron group of group VIII of the periodic table or those in group VHB) of the periodic' table, the -amount is generally higher, usually within the range of from about 1 to about 25% by weight or more of the allumina on a `dry basis. The synthetically prepared alumina-platinum composites are preferentially impregnated with aluminum chloride to form the desired catalysts for use in the hydroisomerization step. This can be accomplishedreadily by sublimation of the aluminum chloride onto the surface of the particles of the platinum-alumina composite. In a like manner, aluminum chloride can be impregnated `on other refractory oxide-hydrogenation component composites. Aluminum chloride sublimes at about 183 C. and thus a suitable impregnation temperature will range from about C. to about 350 C. or higher. The amount of Friedel-Crafts metal halide utilized in preparing these catalysts Will range from about 2.0 to about 25% by weight based on the weight of the refractory oxidehydrogenation metal, more particularly yalumina-platinum, prior to impregnation.

As is readily 'apparent from the description hereinabove, the hydroisomerization step is effected inY a hydrogen atmosphere. Suicient hydrogen should be utilized so that the hydrogen to hydrocarbon ratio of the hydroisomerization zone feed will Vbe within the molar range `of, from aboutA 0.25 to about l0. The hydroisomerizationV step in this'process 'is hydrogenv Yconsuming and this consumption of hydrogen is readily furnished by supplying hydrogen from the dehydrogenation step as set forth hereinafter. Y l

Thel hydroisomerization step of thepres'ent processmay be carried out at varying conditions of temperature, pressure, space velocity, and combined feed ratio. The temperature utilized will generally be dictated by the particular catalyst selected. Inlthe presence ofthe preferred catalyst, the temperature will range from about 200 to about 550 F., although temperatures within the more limited range of from about 300 to about 500 F. will generally be utilized. The pressure selected will depend upon the particular temperature utilized and will range from about 100 to about 1000 pounds per square inch or more. The liquid hourly space velocity will range from about 0.1 to about 10 or more, the only limitation being that equilibrium mixtures of isomerized hydrocarbons or a close approach thereto shall be obtained in the hydroisomerization reaction zone eiliuent. The combined feed ratio which is dened as the total amount of fresh feed entering the reactor and recycle divided by the quantity of fresh feed will range from one up to about or more. Values in between these two apparent limitations are determined by the concentration of cyclohexane in the hydroisomerization reaction zone eluent and further by the concentration of desired high octane number hydrocarbons.

Various dehydrogenation catalysts are utilizable in the dehydrogenation reaction zone -in the process of this invention. These dehydrogenation catalysts normally include -a dehydrogenation component deposited on an acidfree support. 'Ihe dehydrogenation component is preferentially metallic and as such is selected from among the metals of group VIII of the periodic table including iron, cobalt, nickel, platinum, palladium, ruthenium, rhodium, osmium, and iridium. In some instances `the so-called metal oxide dehydrogenation components are also suitable including metal oxides of the -above mentioned group VIII metals as well as the metal oxides of group VI(B) such as chrornia, molybdena, and tungsten oxide. These metallic and metal oxide dehydrogenation components are composited with -a suitable acid-free support in the preferred embodiment. These acid-free supports include silica, alumina, and various naturally occurring substances such as bauxite, kaolin or clay, etc. Of these various supports, alumina is preferred, and particularly preferred is synthetically prepared gamm-a-alumina of a high degree of purity. 'I'he quantity of dehydrogenation component composited with the support usually ranges from about one yto about 25% or more based on the dry weight of the support. When the metallic dehydrogenation component is one of the platinum group metals, the quantity utilized is usually less, for example, from about 0.1 to `about 2% by Weight of the support since these metallic dehydrogenation components are not only expensive but also relatively scarce.

The dehydrogenation step of the process of the present invention may be carried out at varying conditions of temperature, space velocity, and pressure. Here again, the temperature will generally be dictated by the particular catalyst selected. Since the metallic dehydrogenation catalysts are also hydrogenation catalysts, they must be utilized at sufficiently high temperatures so that dehydrogenation is the favored reaction. Such temperatures may range from -about 500 F. to about 1000 F. or more.

The pressure will range from about atmospheric to about 500 pounds per square inch or more. Obviously, the pressure utilized will be as low as possible since lower pressures favor Ithe desired dehydrogenation reaction. Liquid hourly space velocity will range from about 0.1 to about 100 or more. Dehydrogenation of naphthenes containing six carbon atoms in the ring is an exceedingly rapid reaction and thus much higher space velocities can be utilized than are operable for the hydroisomerization reactions. These higher space velocities result in the necessity for 'the utilization of smaller quantities of catalyst in the dehydrogenation reaction zone and thus are favored. Liquid hourly space velocities of from about 5 to about 50 are preferred.

The process of the present invention can perhaps be best understood by reference to the accompanying drawing which is a schematic diagram of the process flow. Referring to the drawing, a'saturated hydrocarbon greater than about 80, for example, a hexane fraction separated from a straight run or catalytically reformed naphtha, is passed, as a liquid under pressure, through` lines 1 and 3 to the upper portion of fractionation zone 4.= The hydrocarbon fraction passing through lines 1 and 3y is combined in line 1 With recycle reaction zone eiuent from line 2 -as hereinafter set forth. Ihe combined feed Ito fractionator 4 is fractionated therein to separate a substantially dehydrogenat-able cycloparan-free overhead from dehydrogenatable cycloparains which occur in the feed or which may be produced during processing by hydroisomerization. Ordinarily these dehydrogenatable cycloparans, such as cyclohexane, occur in the feed and their ydestruction via hydrocracking is prevented by removal at this point. Thus, the hydrocarbon stream from line 3 is fractionated in fractionation zone 4 and the subs-tantially dehydrogenatable cycloparaflin-free portion thereof separated overhead. This cyclohexane-free hydrocarbon fraction passes through line 5, is condensed in condenser 6, `and passes through line 7 to overhead receiver 8. The substantially dehydrogenatable cycloparain-free hydrocarbons from receiver 8 are withdrawn therefrom .through line 9 by pump 10 which discharges into line 11 and supplies reflux to fractionation zone 4 by means of line 12. The net substantially dehydrogenatable cycloparafln hydrocarbon stream from fractionation zone 4 passes from line 11 through line 13 to fractionation zone 21 as hereinafter described. Fractionation zone 4 is heated by reboiling a portion of the dehydrogenatable cycloparaiiins from the bottom thereof which are Withdrawn through lines 14 and 15, and are passed through heat exchanger 16. The heated hydrocarbons are then returned to a lower portion of fractionation zone 4 lthrough line 17. The higher boilingv dehydrogenatable cyclopara'in bottoms fraction is withdrawn from the bottom of fractionation zone 4 through lines 14 and 18 by pump 19 and is pumped through line 20 to the dehydrogenation step hereinafter described.

The purpose of fractionation zone 21 is to fractionate the feed thereto to produce a hydrocarbon fraction ch-aracterized by -a major proportion of hydrocarbons which contain at least two methyl substituents per molecule and to produce a 4hydroisomerization reaction zone feed. The overhead product from fractionation zone 21 thus comprises dimethylalkanes naturally occurring in the feed and dimethylalkanes from the reaction zone eiuent which have been formed as a result of the hydroisomerization of normal parains and monomethylalkanes `as set forth hereinafter. For example, when processing a hexane fraction, the overhead product which is separated from the process at this point comprises 2,2- and 2,3-dirnethyl butanes naturally occurring in .the feed Iand 2,2- and 2,3- dlmethylbutanes from the hydroisornerization reaction zone eilluent which have been formed as a result of the hydroisomerization of normal hexane and 2- and 3- methylpentane as set forth hereinafter. Also, any Water which. is dissolved in the feed or produced during the hydrorsomerization processing separates overhead at this point due to distillation drying. Therefore, the bottoms from fractionation zone 21 which pass to the hydroisomerization reaction zone are for all practical purposes substantially water free. The above described dimethyllalkane hydrocarbon stream passes from fractionation zone 21 overhead through line 22, is condensed in condenser 23, and passes through line 24 to overhead receiver 25: From receiver 25, the hydrocarbon fraction passes through line 26 to pump 27 which discharges into line 28 and pro-` vides reux for fractionation zone 21 by means of line 29. The net dimethylparain hydrocarbon stream is withdrawn through line 30. Water which is separated overhead by distillation drying in fractionation zone 21 is removed from overhead receiver 25 by drain line 31. Fractionator 21 is heated by reboiling a portion-of the higher boiling hydrocarbons, which are Withdrawn therefrom ansa-,vis

'l through 32 and 33 and are. passed through heat exchanger 34. The heated'hydrocarbons are then returned into a lower portion of fractionation zone 21 through line 35. The higher boiling hydrocarbons, substantially free from dehydrogenatable cycloparafns as hereinabove de' scribed, and substantially free'from dimethylalkanes, are withdrawn from fractionation zone 2.1 through lines 32y and 36 b-y pump 37. Y

The net hydrocarbon s-tream from fractionation zone 21 is-passed by pump 37 through lines 38 and 39. From line 39 this hydrocarbon stream is heat exchanged With the hot reaction zone efuent lin heat exchanger 40 and then passes through line 41 to heater 42. In heater 42, the stream is heated to the desired reaction temperature, and then passes through line 43 to hydroisomerization reaction zone 44. Itis in this Ireaction zone 44 that the less highly branched Vchain and straight chain hydrocarbons and naphthenes containing tive carbon atoms in the ring are isomerized to an equilibriummixture of saturated hydrocarbon isomers; As will be set forth hereinafter, the hydrocarbons are processed in the presence of hydrogen which is introduced via line 53 into line 39. This hydrogen also hydrogenates any aromatic hydrocarbons in reaction zone 44.

The conditions utilized in hydroisornerization reaction zone 44 will depend upon the particular hydroisomerization catalyst utilized therein. It was pointed out above that a preferred catalyst in the process of this invention is one comprising a hydrogenation component deposited on an acid-acting support. With such a catalyst, the pressure utilized will range from about 100 to about 1000 pounds per square inch, the temperature will range from about 200 to about 500 F., and the hourly liquid space velocity will range from about 0.1 to about 10, The hydrogen to hydrocarbon ratio in the reaction zone Will range from about 0.25 to about l mols of hydrogen per mol of hydrocarbon. When the preferred hydroisomerization catalyst comprising platinum and alumina which has been impregnated with a Friedel-Crafts metal halide, such as aluminum chloride, is utilized, the temperaturc will be in the preferred range of from about 300 to about 500 F. In some instances it is desirable and/or advisable to utilize hydrogen halide along with these catalysts and thus the use of hydrogen chloride, for example, is within the generally broad scope of the present invention.

The hydroisomerization reaction zone effluent passes from reactor 44 through line 45 in indirect heat exchange with the hydroisomerization reaction zone feed through heat exchanger 40 and then passes through line 46, is condensed in condenser 47, and passes through line 48 to high pressure separator 49. The high pressure separator 49 is utilized for separating hydrogen from the isomer-ized hydrocarbons, Which hydrogen is separated and passed through lines 50 and 51 to compressor 52 whereits pressure is increased to the desired number of pounds per square inch, and then the hydrogen is discharged through `line 53 as hereinabove described. When a hydrogen halide is utilized along with the hereinabove described catalyst las a promoter, a substantial proportion of it Will pass through lines 50 and 51 to compressor 52 as hereinabove described.

Makeup hydrogen, to maintain the process Yin hydrogen balance, is supplied to the hydroisomerization zone through line 79 from dehydrogenation as hereinafter described. This makeup hydrogen passes from line 79 to line 51 wherein it joins the recycle hydrogen from line 50, both hydrogen streams then being compressed by compressor 52. As stated hereinabove, hydrogen consumption in the hydroisomerization process of the present invention is relatively small, tha-t is less than 100 cubic feet of hydrogen per barrel of combined feed to the hydroisomerization reaction zone, and usually this consumption isl less than 50 cubic feet of hydrogen per barrel. inra normal operation,` thisV 50 cubic feety perbarriel is divided betweenhydrogen consumedby reaction with hydrocarbons and sludge, if any, and hydrogen lost through solubility in the euentifrom the high pressure separator. The loss due to solubility may runV in the order of about 30 cubic'feet of hydrogen per barrel and thus about 20 cubic feet vof hydrogen per barrel can be assigned to reactions; The cooled hydroisomerization zone efuent after high pressure Y'separation is discharged fromV separator 49 through line 54 to debutanizer 5S. This debutanizer is a conventional fractionation zone by means ofy which light' hydrocarbon gas or low boiling cracked products and dissolved hydrogen-are removed from the process. ThisV removal is 'accomplished through line 56 which may include receiver and reflux means not shown. Debutanizer 55 is heatedby passing a portion of the higher boiling hydrocarbons Ythrough lines 57 and 58 to hea-t exchanger 59 from'which'the heated hydrocarbons are returned to alower portion of debutanizer 55 via line V60. The net hydroisomerization reactionrzone efuent is Withdrawn from debutanizer 55 through lines 57 and '61 by means of pump 62 which discharges the liquid hydroisomerization reaction zone effluent through line 2 to fractionator 4 for fractionation as described hereinabove.

As set forth hereinabove, the dehydrogenatable cycloparain hydrocarbon fraction, for example, cyclohexane, is Withdrawn from the kbottom of fractionation zone 4 through lines 14 and 18 by means of pump 19 which discharges this dehydrogenatable cycloparan hydrocarbon fraction into line 20. From line 20 these dehydrogenatable cyclopar-ain hydrocarbons are passed to heater 63 in which this stream is heated tothe desired reaction temperature, and then passes through lines 64 and 65 to dehydrogenation reaction zone 66. It is in this dehydrogenation reaction zone`66 that thedehydrogenatable cycloparatlin hydrocarbons are dehydrogenatcd to Varomatic hydrocarbons and hydrogen; While usually not desired since it tends to reverse the desired direction of the reaction, these dehydrogenatable cycloparain hydrocarbons m-ay be dehydrogenated in the presence of hydrogen which is introduced via lines 74 and 76 into line 65. Some hydrogen may be desirable, depending upon the particular catalyst utilized since the hydrogen may tend to reduce or prevent carbon deposition on the catalyst in dehydrogenation zone 66.

The conditions utilized in dehydrogenation reaction zone 66 will depend upon the particular dehydrogenation catalyst utilized therein. With catalysts of the type set forth hereinabove, the pressure utilized in the reaction zone Will range from atmospheric to about 500 pounds per square inch or more, the temperature will range from about 500 to about 1000 F. or more, and the hourly liquid space velocity will range from about 0.1 to about or more. A particularly preferred catalyst comprises platinum deposited Yon an acid-free support such as platinum-alumina in which the platinum content ranges from about y0.01 to about 2.0% by Weight. The temperature utilized will be from about 750 to about 900 Fjwith such a catalyst. Also, the hourly liquid space velocity will be from about 5 to about 50. 'Low pressures are always most desirable.

The dehydrogenation reaction zone effluent passes from reactor 66 through line 67, is condensedv n condenser 68, and passes through line 69 to high pressure separator 70. High pressure separator 70 is utilized for separatinghydrogen from the aromatic hydrocarbons produced in the dehydrogenation reaction zone. This hydrogen is separated and passed throughline 771 to compressor 72`which discharges through line 73 connected to lines 74 and 77. Line 74 contains pressure control valve 75 which is set so that the desired amount of hydrogen, if any, passes therethrough to lines 76 and 65 as set forth hereinabove. As is readily apparent, the major proportion of the hydrogen isv discharged from compressor 72 through lines 73 and 77. Line 77 containsrpressure control valve 78 which is set softhat thedesired amount of hydrogen is passed from line 77 through line 79 to the hydroisomerization reaction zone as set forth hereinabove, and so that the remainder of the hydrogen is vented. In this manner, the combination process is self suicient in hydrogen, and makeup hydrogen, if necessary, is supplied to the hydroisomerization reaction zone in a quantity to balance the amount consumed during the reaction and dissolved in the liquid withdrawn from high pressure separator 49. The aromatic hydrocarbon fraction, such as benzene, is withdrawn from high pressure separator 70 through line 80.

The following example is introduced solely for the purpose of illustration and with no intention of unduly limiting the generally broad scope of this invention.

Example One speciiic example of the operation of the process with a platinum-alumina-aluminum chloride catalyst in the hydroisomerization reaction zone and a platinumalumina catalyst in the dehydrogenation zone and as the process is carried out similar to that set forth hereinabove With reference to the drawing is described herewith now in connection with the drawing. The catalyst utilized in the hydroisomerization reaction zone comprises alumina containing 0.4% platinum, said composite having been impregnated with about 17% by weight of aluminum chloride. The catalyst utilized in the dehydrogenation reaction comprises alumina containing V0.7% platinum.

This example illustrates the production of dimethylbutanes via hydroisomerization and the production of benzene and hydrogen via dehydrogenation from a Gulf Coast hexane fraction, boiling point 4074 C. The composition of this Gulf Coast hexane fraction is as follows: cyclopentane, 3%; 2,2-dimethylbutane, 3%; 2,3- dimethylbutane, 2-methylpentane, 25%; 3-methylpentane, 20%; normal hexane, 30%; methylcyclopentaue, 3%; dimethylpentanes, 1%; cyclohexane, 7%; and benzene, 3%. By this process there is produced from 1000 barrelsV per day of this hexane fraction 860 barrels per day of a fraction comprising mainly dimethylbutanes and somewhat less than 140 barrels per day of benzene containing a small amount of dimethylpentanes, this difference in volume being accounted for by shrinkage due to the change in specific gravity from cyclohexane to benzene. Referring again to the drawing, this hexane fraction, having an average molecular weight greater than 80, in the quantity of 1000 barrels per day, is passed as a liquid under pressure through line 1 and through line 3 to an upper section of fractionation zone 4. This fresh feed stream has combined therewith in line 1, 2430 barrels per day of recycle hydroisomerization reaction zone efuent from line 2 as hereinafter described. This recycle hexane stream consisting of the liquid hydroisomerization reaction Yzone efuent contains 504 barrels per day of 2,2-dimethylbutane, 246 barrels per day of 2,3- dimethylbutane, 795 barrels per day of Z-methylpentane, 445 barrels per day of 3-methylpentaue, 350 barrels per day of normal hexane, 60 barrels per day of methylcyclopentane, and 30 barrels per day of cyclohexane. Thus, the total combined feed to fractionation zone 4 amounts to 3430 barrels per day comprising 30 barrels per day of cyclopentane, 534 barrels per day of 2,2-dimethylbutane, 296 barrels per day of 2,3-dimethylbutane, 1045 barrels per day of Z-methylpentane, 645 barrels per day of S-methylpentane, 650 barrels per day of normal hexane, 90 barrels per day of methylcyclopentane, l0 barrels per day of dimethylpentane, 100 barrels per day of cyclohexane, and 30 barrels per day of benzene. The combined feed to fractionation zone 4 is fractionated therein under a 2: 1 molal reux to feed ratio and a substantially cyclohexane-free stream is separated overhead therefrom in the amount of 3290 barrels per day. This 3290 barrels per day contains 30 barrels per day of cyclopentane, 534 barrels per day of 2,2-dimethylbutane, 296 barrels per day of 2,3-dimethylbutane, 1045 barrels per day of Z-methylpentane, 645 barrels per day of 3-methy1- pentane, 650 barrels per day of normal hexane, and barrels per day of methylcyclopentane. This fractionation zone 4 overhead is withdrawn therefrom through line 5, is condensed in condenser 6, and is passed through line 7 to overhead receiver 8. Prom receiver 8 the liquid is Withdrawn through line 9 by pump 10 which supplies feed to a fractionation zone 21, hereinafter described, via line 13.

Fractionation zone 4 bottoms are withdrawn from line 14 through line 8 by pump 19 and have a composition as follows: 10 barrels per day Vof dimethylpentanes, 100 barrels per day of cyclohexane, and 30 barrels per day of benzene. These bottoms are then pumped by pump 19 through line 20 to heater 63 and dehydrogenation, described hereinafter.

' The feed stream to fractionation zone 21 in the quantity of 2350 barrels per day of the composition described hereinabove is fractionated therein under a 4:1 molal reflux to feed ratio and the overhead passed therefrom through line 22, condensed in condenser 23, and is passed las a liquid through line 24 to overhead receiver 25. Fractionation zone 21 separates a substantially monomethylpentane and normal hexane-free dimethylbutane stream overhead therefrom in an amount of 860 barrels per day. This 860 barrels per day contains 30 barrels per day of cyclopentane, 534 barrels per day of 2,2-dimethylbutane, and 296 barrels per day of 2,3-dimethylbutane. This stream has an F-l clear octane number of 96.4 and an F-l-l-3 cc. octane number of 111.1. This fractionation zone overhead is withdrawn from receiver 24 through line 26 by pump 27 and the net product is pumped through lines 28 and 30 to storage.

The substantially dimethylbutane-free bottoms stream from the fractionation zone 21 in the quantity of 2430 barrels per day is the hydroisomerization reaction zone feed. The composition of this stream is as follows: `1045 barrels per day of Z-methylpentane, 645 barrels per day of 3-methylpentane, 650 barrels per -day of normal hexane, and `90 barrels per day of methylcyclopentane. 'Ihis bottoms stream from fractionation zone 21 is withdrawn therefrom through lines 32 and 36 by means of pump 37 which pumps this stream through lines 38 and 39, where it is joined With hydrogen from line 53, through heat exchange zone 40, to line 41 and heater 42.'. The quantity of hydrogen which is continuvously supplied is sufficient to maintain a hydrogen to hydrocarbon ratio of 2:1 in the hydroisomerization zone. 'I'his is accomplished by recycling hydrogen from the high pressure separator and from the dehydrogenation zone as hereinafter described back to the hydroisomerization zone. 'I'he quantity of hydrogen which is supplied from the dehydrogenation zone as hereinafter described is that necessary to make up for the hydrogen consumed in the reaction and for the hydrogen which is dissolved in the high pressure separator liquid eiuent. By means of heat exchanger 40 and heater 42 the combined feed to the reaction zone is heated to a temperature of about 340 F. The reaction is carried out at a pressure of about 500 p.s.i.g. in vapor phase at a liquid hourly space velocity of about 2.0. As set forth hereinabove, hydroisomerization of this feed is `accomplished in reaction zone 44 in the presence of the hereinabove described hydroisomerization catalyst and results in the production of 2340 barrels per day of reaction zone eiuent containing 504 barrels per day of 2,2-dimethylbutane, 246 barrels per day of 2,3-dimethylbutane, 795 barrels per day of Z-methylpentane, 445 barrels per day of 3-methylpentane, 350 barrels per day of normal hexane, 60 barrels per day of methylcyclopentane, and 30 -barrels per day of cyclohexane.

The hydroisomerization reaction zone euent after heat exchange with the incoming feed is passed via lines 45 and 46 to condenser 47, and the liquid product and hydrogen gas are then passed through line 48 to high pressure 'separatori 49.1;Tl1`eV hydrogen gas`ialong' ywitl minor amounts of low boiling,hydrocarbonsY formed by cracking in the reaction zone are separated in high `pres` sure separator 49 and passed through lines 50 and 51 to compressor 52. High pressure separator liquid'vvhich discharges through line 54 is passed to 'tdebutanizer 5S to further separate this small amount of cracked products produced during hydroisomerization and .to prepare the liquid recycle stream 'as hereinabove set forth.V 'The' liquid recycle stream passes from debutanize'r 55 through lines 57 and 61 to pump 62 lwhereinl it is recycled to fractionation zone 4 via line 2.

' As stated hereinabove, the bottoms from fractionation zone 4 are Withdrawn therefrom through lines 14 and 18 by pump 19 from which these bottomspass through line 2'0 to heater 63. These bottoms comprising 10 barrels per day'of dimethylpentanes, 100 barrels perY day of cyclohexane, and barrels per day ofibenzen'e are heated to 800 F. in heater 63 and are passed therefrom via lines 64 and `65Vto dehydrogenationreaction zone 66. The dehydrogenation reaction is carried outat apressvure of about 100 p.s.i.g. in vapor phase at an hourly liquid space velocity of 10. As set forth hereinabove, dehydrogenation ofthe dehydrogenation reaction zone feed israccomplished in dehydrogenation zone 66 in the presence of the hereinabove described catalyst and results in the production of approximately 140 barrels per inea Vhydrogen production' of 4.43)(105 standard cubic feet of hydrogerrpe'r day. With a normal consumption of hydrogen in the'hydroisomerizationzone of V50 cubic feet of Vhydrogen per barrel, approximately 4.3)(104 standard cubic feet of hydrogen per day passfrom line 77 through line 79 back to the hydroisomerization reactor. The remainder of the hydrogen produced, approximately 4 105 standard cubic feet of hydrogen per day, is vented from line 77. f Y' The above example illustrates the production of 860 barrels per day of a hydrocarbon fraction comprising dimethylbutanes'having an F-l clear octane number of 96.4 and an F-l-l-'S Vec. octane number'of 111.1, and the simultaneous production 'of approximately 140 barrels per day of benzene.Y` In the above example, the small amount of cracking which is observed during processing has` not beentakeninto account. This can be done since the liquid volume yields through the hydroisomerization reactor are in the order of 98 volume percent or higher, and the liquid volume yields through the dehydrogenation reactor are approximately 100% except for the loss due to volumetric shrinkage due to the diiference in the specific gravity of the feed and the product from the dehydrogenation reactor.

The volume balances in barrels per day in and out of the 1000 barrel per day process exemplied here iuabove are presented in the following Table III:

TABLE III Bbls./Day

Hydro- Frac- Fracs Hydro- Dehy- Dehyisomeritionationaisomeridrogendrogen- Fresh zation tion tion ration ation ation Feed Zone Zone Zone Zone Zone Zone Eiuent Bottoms Over- Feed Feed Etluent head 30 60 10 10 10 10 Cyelohexaue 70 30 100 Y 100 VBirmania 30 30 30 130 day of reaction zone emuent containing 10 barrels per day of dimethylpentanes and labout 130 barrels per day of benzene. The dehydrogenation of the hundred barrels per day of cyclohexane in the vfeed to the dehydrogenation reaction zone results -in the production of 4.43 X105 standard cubic feet of hydrogen per day.

The dehydrogenation Vreaction zone efuent is withdrawn from dehydrogenation zone 66 throughline 67 torcondenser 68, and the liquid product and hydrogen gas fare then passed through line 69 to high pressure separator 70. The hydrogen gas producedin dehydrogenation zone 66, except for that dissolved in the benzene, is Withdrawn from high'pressure separator 70 through line 71 by compressor 72 which discharges into line 73.

From line 73 this hydrogen or a portion thereof, if so desired, may beV directed to the dehydrogenation re. action zone -by an appropriate setting of` valve 75 and thus the hydrogen Will pass through liners` 73,74, 76, and 65 back to dehydrogenation zone l66. In the usual case, valve 75 will be closed and the hydrogen which is discharged from the compressor Will pass through lines 73, 77, and 79. Valve 78 in line 77 will be set so that sucient hydrogen passes from line 77 through lineY 79 back to the hydroisomerization zone 44 to maintain the combination process inV hydrogen balance. The rremainder of the hydrogen is vented from line 77 to other uses not shown. As stated hereinabove, -th'edehydrogention .of ybarrels* per day Vof'cyclohexane results As is shown in the above table, the high octane number product is the 860 barrels per day of fractionation zone 21 overhead. The benzene product is the 140 barrels per day of dehydrogenation Zone effluent. In addition to the two above products there is also vented from the process in this example approximately 4 l05 standard cubic feet of hydrogen per day. All this results from feeding to the process 1000 barrels per day of a hexane hydrocarbon fraction shown in the table as the fresh feed.

` I claim as my invention: u

1. A combination hydroisomerization and dehydrogenation process for the simultaneousproduction of dimethylbutanes and benzene, said process self-sufficient in hydrogen requirement, which' comprises passing to a rst fractionation zone an isomeriz'able hexane hydrocarbon fraction in combination with liquid phase hydroisomerization zoneV eiuent produced as hereinafter described, fractionating said hydrocarbons to produce a substantially cyclohexanefree overhead hydrocarbon fraction and to vproduce a substantially pure cyclics hydrocarbon bottoms fraction comprising" cyclohexane, passing said cyclohexane bottoms fraction to a dehydrogenation zone hereinafter described, passing said substantially cycloheXane-free overhead hexane fraction from'said first fractionation zone toV a second fractionation zone as feed therefor, fractionating said hydrocarbons ,to produce 75 ,3.1.1 overhead hydrocarbon fraction containing 2,2- and2,3

dimethylbutanes and to produce a bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes as one product from the process, passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane along with hydrogen at least some of which is produced by dehydrogenation as hereinafter described to a hydroisomerization zone maintained at a temperature of from about 300 F. to about 500 F. and at a pressure of from about 100 to about 1000 pounds per square inch wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a liquid hourly space velocity of from about 0.1 to about in the presence of a hydroisomerization catalyst comprising a hydrogenation component deposited on an acid-acting support to an equilibrium mixture of hexane hydrocarbons including 2,2- and 2,3-dimethylbutanes, methylpentanes, normal hexane, methylcyclopentane, and cyclohexane, recycling the hydroisomerization zone effluent to the irst mentioned fractionation zone as aforesaid to recover cyclohexane therefrom and to allow recovery therefrom of 2,2- and 2,3-dimethylbutanes produced in the process in said second fractionation zone as aforesaid and to separate methylpentanes, normal hexane, and methylcyclopentane as aforesaid for reuse and internal recycle in said process, dehydrogenating said cyclohexane from the bottom of said first fractionation zone in a dehydrogenation zone in the presence of a dehydrogenation catalyst at dehydrogenation conditions to produce hydrogen and benzene, removing said benzene as the second product from the process, and recycling at least a portion of said hydrogen to the hydroisomerization zone as the sole source of makeup hydrogen therefor.

2. A combination hydroisomerization and dehydrogenation process for the simultaneous production of dimethylbutanes and benzene, said process self-sufhcient in hydrogen requirement, which comprises passing to a rst fractionation zone an isomerizable hexane hydrocarbon fraction in combination with liquid phase hydroisomerization zone eiuent produced as hereinafter described, fractionating said hydrocarbons to produce a substantially cyclohexane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising cyclohexane, passing said cyclohexane bottoms fraction to a dehydrogenation zone hereinafter described, passing said substantially cyclohexane-free overhead hexane fraction from said first fractionation zone to a second fractionation Zone, fractionating said hydrocarbons to produce an overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes and to produce 4a bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said overhead hydrocarbon fraction containing 2,2-V and 2,3-dimethylbutanes as one product from the process, passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane along with hydrogen at least some of which is produced by dehydrogenation as hereinafter described to a hydroisomerization zone maintained at a temperature of from about 300 F. to about 500 F. and at a pressure of from about 100 to about 1000 pounds per square inch wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a liquid hourly space velocity of from about 0.1 to about 10 in the presence of a hydroisomerization catalyst comprising a hydrogenation component deposited on an acid-acting support to an equilibrium mixture of hexane hydrocarbons including 2,2- and 2,3-dimethylbutanes, methylpentanes, normal hexane, methylcyclopentane, and cyclohexane, recycling the hydroisomerization zone effluent to the rst mentioned fractionation zone as aforesaid to recover cyclohexane Itherefrom and to allow recovery therefrom of 2,2- and 2,3-dimethylbutanes produced in the process in said second fractionation zone as aforesaid and to separate methylpentanes, normal hexane, and methylcyclopentane as aforesaid for reuse and internalrecycle in said process, dehydrogenating said cyclohexane from the bottom of said first fractionation zone in a dehydrogenation zone in the presence of a dehydrogenation catalyst at a temperature of from about 500 F. to about 1000 F., a pressure of from about atmospheric to about 500 pounds per square inch, and at a liquid hourly space velocity of from about 0.1 to about to produce hydrogen and benzene, removing said benzene as the second product from the process, and recycling at least a portion of said hydrogen to the hydroisomerization zone as the sole source of makeup hydrogen therefor.

3. A combination hydroisomerization and dehydrogenation process for the simultaneous production of dimethylbutanes and benzene, said process self-sufficient in hydrogen requirement, which comprises passing to a first fractionation zone an isomerizable hexane hydrocarbon fraction in combination with liquid phase hydroisomerization zone effluent produced as hereinafter described, fractionating said hydrocarbons to produce a substantially cyclohexane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising said cyclohexane bottoms fraction to a dehydrogenation zone hereinafter described, passing said substantially cyclohexane-free overhead hexane fraction from said rst fractionation zone to a second fractionation zone as feed therefor, fractionating said hydrocarbons to produce ran overhead hydrocarbon fraction containing 2,2 and 2,3-dimethylbutanes and to produce a bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said overhead hydrocarbon fraction containing 2,2- and 2,3- dimethylbutanes as one product from the process, passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane along with hydrogen at least some of which is produced by dehydrogenation as hereinafter described to a hydroisomerization zone maintained at a tempera-ture of from about 300 F. to about 500 F. and at a pressure of from about 100 to about 1000 pounds per square inch wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a liquid hourly space velocity of from about 0.1 to about 10 in the presence of a hydroisomerization catalyst comprising a platinum group metal deposited on a refractory oxide support impregnated with a Friedel-Crafts metal halide to an equilibrium mixture of hexane hydrocarbons including 2,2- and 2,3-dimethylbutanes, methylpentanes, normal hexane, methylcyclopentane, and cyclohexane, recycling the hydroisomerization zone effluent to the i'irst mentioned fractionation zone as aforesaid to recover cyclohexane therefrom and to allow recovery therefrom of 2,2- and 2,3-dimethylbutanes produced in the process in said second fractionation zone as aforesaid and to Separate methylpentanes, normal hexane, and methylcyclopentane as aforesaid for reuse and internal recycle in said process, dehydrogenating said cyclohexane from the bottom of said rst fractionation zone in a dehydrogenation zone in the presence of a metallic dehydrogenation catalyst comprising a dehydrogenation component deposited on an acid-free support at a temperature of from about 500 F. to about 1000 F., a pressure of from about atmospheric to about 500 pounds per square inch, and at a liquid hourly space velocity of from about 0.1 to about 100 to produce hydrogen and benzene, removing said benzene as the second product from the process, and recycling at least a portion of said hydrogen to the hydroisomerization zone as the sole source of makeup hydrogen therefor.

4. A combination hydroisomerization and dehydrogenation process for the simultaneous production of dimethyl butanes and benzene, said process self-suicient in hydrogen requirement, which comprises passing to a first fractionation zone an isomerizable hexane hydrocarbon fraction in combination with liquid phase hydro` isomerization zone eiuent produced as hereinafter described, fractionating said hydrocarbons to produce a substantially cyclohexane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising cyclohexane, passing said cyclohexane bottoms fraction to a dehydrogenationv zone hereinafter described, passing said substantially cyclohexane-free overhead hexane fraction from said first Vfractionation zone to a second fractionation zone as feed therefor, fractionating said hydrocarbons to produce an overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes and to produce a bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanesV as one product from the process, passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane along with hydrogen at least some of which is produced by dehydrogenation as hereinafter described to a hydroisomerization zone maintained at a temperature of from about 300 F. to about 500 F. and at a pressure of from about 100 to about 1000 pounds per square inch wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a liquid hourly space Velocity of from about 0.1 to about in the presence of a hydroisomerization catalyst comprising platinum deposited on lalumina impregnated with aluminum chloride to an equilibrium mixture of hexane hydrocarbons including 2,2- and 2,3-dimethylbutanes, methylpentanes, normal hexane, methylcyclopentane, and cyclohexane, recycling the hydroisomerization zone effluent to the first mentioned fractionation zone as aforesaid to recover cyclohexane therefrom land to allow recovery therefrom of 2,2- and Z-dimethylbutanes produced in the process in said second fractionation zone as aforesaid and to separate methylpentanes, normal hexane, and methylcyclopentane as aforesaid for reuse and internal recycle in said process, dehydrogenating said cyclohexane from the bottoms of said irst fractionation zone in a dehydrogenation zone in the presence of a dehydrogenation catalyst comprising platinum deposited on an acid-free support at a temperature of from about 500 F. to about l000 F., a pressure of from about atmospheric to about 500 pounds per square inch, and at a liquid hourly space velocity of from about 0.1 to `about 100 to produce hydrogen and benzene, removing said benzene as the second product from the process, `and recycling a-t least a portion of said hydrogen to the hydroisomerization zone as the sole source of makeup hydrogen therefor.

5. A combination hydroisomerization and dehydrogenation process for the simultaneous production of dimethylbutanes and benzene, said process 'self-sucient in hydrogen requirement, which comprises passing to a lirst fractionation zone an isomerizable hexane hydrocarbon fraction in `combination with liquid phase hydroisomerization zone effluent produced as hereinafter described, fractionating Said hydrocarbons to produce a substantially cyclohexane-freeroverhead hydrocarbon 'action and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising cyclohexane, passing said cyclohexane bottoms fraction to a dehydrogenation zone hereinafter described, passing said substantially cyclohexanefree overhead hexane fraction from `said iirst'fractionation zone to a second fractionation Zone as feed therefor, fractionating said hydrocarbons to produce an overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes and to produce a bottoms hydrocarbon'fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes as one'product' from the process, passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane, Yand methylcyclopentane Yalong* 'withhy- CJI drogen at least `some. vof which is Yproduced by dehydrogenationas hereinafter described to a hydroisomerization zone maintained at a temperature of fromabout 300 F.-

to about 500 and at a pressure of from about 100 to about 1000 pounds'per square-inch wherein `methylpentanes, normal hexane, and methylcyclopentane are isomerized at a Vliquid hourly space velocity of kfrom about 0.1 `to Vabout l0 in the presence of a hydroisomerization catalyst comprising platinum depositedon alumina impregnated with aluminum chloride to an'equilibrium mixture of hexane hydrocarbons including 2,2- and 2,3- dimethylbutane, methylpentanes, normal hexane,'methyl cyclopentane, and cyclohexane, recyclingthe hydroisomerization zone eiuent to the rst mentionedfractionation zone as aforesaid torecover cyclohexane therefrom and to allow recovery thereom of 2,2- andV 2,3-dimethylbutanes produced inthe process in said second fractionation zone as aforesaid and toV separate lmethylpentanes, normal hexane, and methylcyclopentane asl aforesaid for reuse `and internal recycle in said process,Y dehydrogenating said cyclohexane from the bottoms of said first fractionation zone in a dehydrogenation zonein the presence of a platinum-alumina dehydrogenation catalyst at a temperature of from about 500 F. to about 1000 F., a pressure of from about atmospheric to about 500 pounds per square inch, and at a liquid hourly space velocity of from about 0.1 -to about to produce hydrogen and benzene, removing said benzene as ythe second product from the process, and recycling at least a portion of said hydrogen to the hydroisomerizationzone asthe sole source of makeup hydrogen therefor.

6. A combination hydroisomerization and dehydrogenation process for'the simultaneous production of dimethylbu-tanes and benzene, said process self-suiiicient in hydrogen requirement, which comprises passing to a rst fractionation zone an isomerizable hexane hydrocarbon fraction in combination with liquid phase hydroisomerization Zone effluent produced as hereinafter described, fractionating said hydrocarbons to produce a substantially cyclohexane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising cyclohexane, passing said cyclohexane bottoms fraction to a dehydrogenation zone hereinafter described, passing said substantially cyclohexane-free overhead hexane fraction from said rst lfractionation zone to a second fractionation zone `as feed therefor, fractionating said hydrocarbons to produce au ovehead hydrocarbon fraction containing 2,2- and 2,3- dimethylbutanes and to produce a bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said 'overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes as one product from the process, passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane along with hydrogen at least some of which is produced by dehydrogenation as hereinafter described to v'a hydroisomerization zone maintained at a temperature of from about 300 F. to about 500 F. and at a pressure of from about 100 to about'1000 pounds per square inch wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a liquid hourly space velocity of from about 0.1 to about l0 in the presence of a hydroisomerization catalyst comprising platinum deposited on alumina impregnated with aluminum chloride to an equilibrium mixture of hexane hydrocarbons including 2,2-'and r2,3-dimethybutanes, methylpentanes, normal hexane, methylcyclopentane, and cyclohexanerecycling the hydroisomerization zone eiuent to the firs-t mentioned fractionation zone as aforesaid to recover cyclohexane therefrom and to allow recovery therefrom of 2,2- and 2,3-dimethylbutanes produced inthe process in said second fractionation zone as VaforesaidV and to separate methylpentanes, normal hexane, and methylcyclopentane as aforesaid for reuse'and internal recycle in said process,` dehydrogenating said cyclohexane from the bottom of said rst fractionation zone in a dehydrogenation zone in the presence of a dehydrogenation catalyst comprising nickel deposited on an acid-free support at a temperature of from about 500 F. to about l000 F., a pressure of from about atmospheric to about 500 pounds per square inch, and at a liquid hourly space velocity of from about 0.1 to about 100 to produce hydrogen and benzene, removing said benzene as the second product from the process, and recycling at least a portion of said hydrogen to the hydroisomerization zone as the sole source of makeup hydrogen therefor.

7. A combination hydroisomerization and dehydrogenation process for the simultaneous production of dimethylbutanes and benzene, said process self-suicient in hydrogen requirement, which comprises passing to a rst fractionation zone an isomerizable hexane hydrocarbon fraction in combination with liquid phase hydroisomerization zone eiiiuent produced as hereinafter described, fractionating said hydrocarbons to produce a substantially cyclohexane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising cyclohexane, passing said cyclohexane bottoms fraction to a dehydrogenation zone hereinafter described, pass said substantially cyclohexanefree overhead hexane fraction from said first fractionation zone to a second fractionation zone as feed therefor, fractionating said hydrocarbons to produce an overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes and to produce a bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said`overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes as one product from the process, passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane along with hydrogen at least some of which is produced by dehydrogenation as hereinafter described to a hydroisomerization zone maintained at a temperature of from about 300 F. to about 500 F. and at a pressure of from about 100 to about 1000 pounds per square inch wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a 'liquid hourly space velocity of from about 0.1 to about in the presence of a hydroisomerization catalyst comprising platinum deposited on alumina impregnated with aluminum chloride to an equilibrium mixture of hexane hydrocarbons including 2,2- and 2,3-dimethylbutanes, methylpentanes, normal hexane, methylcyclopentane, and cyclohexane, recycling the hydroisomerization zone eiuent to the first mentioned fractionation zone as aforesaid to recover cyclohexane therefrom and to allow recovery therefrom of 2,2- and 2,3-dimethylbutanes produced in the process in said second fractionation zone as aforesaid and to separate methylpentanes, normal hexane, and methylcyclopentane as aforesaid for reuse and internal recycle in said process, dehydrogenating said cyclohexane from the bottoms of said rst fractionation zone in a dehydrogenation zone in the presence of a nickel-alumina dehydrogenation catalyst at a temperature of from about 500 F. to about l000 F., a pressure of from about atmospheric to about 500 pounds per square inch, and at a liquid hourly space velocity of from about 0.1 to about 100 to produce hydrogen and benzene, removing said benzene as the second product from the process, and recycling at least a portion of said hydrogen to the hydroisomerization zone as the sole source of makeup hydrogen therefor.

8. A combination hydroisomerization and dehydrogenation process for the simultaneous production of dimethylbutanes and benzene, said process self-sucient in hydrogen requirement, which comprises passing to a rst fractionation zone an isomerizable hexane hydrocarbon fraction in combination with liquid phase hydroisomerization zone eifluent produced as hereinafter described, fractionating said hydrocarbons to produce a substantially cyclohexane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising cyclohexane, passing said cyclohexane bottoms fraction to a dehydrogenation zone hereinafter described, passing said substantially cyclohexanefree overhead hexane fraction from said rst fractionation zone to a second fractionation zone as feed therefor, fractionating said hydrocarbons to produce an overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes and to produce a bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said overhead hydrocarbon fraction containing 2,2- and 2,3-dimethylbutanes as one product from the process, passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane along with hydrogen at least some of which is produced by dehydrogenation as hereinafter described to a hydroisomerization zone maintained at a temperature of from about 300 F. to about 500 F. and at a pressure of from about 100 to about 1000 pounds per square inch wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a liquid hourly space velocity of from about 0.1 to about l0 in the presence of a hydroisomerization catalyst comprising platinum deposited on alumina impregnated with aluminum chloride to an equilibrium mixture of hexane hydrocarbons including 2,2- and 23a-dimethylbutanes, methylpentanes, normal hexane, methylcyclopentane, and cyclohexane, recycling the hydroisomerization zone eflluent to the first mentioned fractionation zone as aforesaid to recover cyclohexane therefrom and to allow recovery therefrom of 2,2- and 2,3-dimethylbutanes produced in the process in said second fractionation zone as aforesaid and to separate methylpentanes, normal hexane, and mcthylcyclopentane as aforesaid for reuse and internal recycle in said process, dehydrogenating said cyclohexane from the bottoms of said first fractionation zone in a dehydrogenation zone in the presence of a nickel-kieselguhr dehydrogenation catalyst at a temperature of from about 500 F. to about l000 F., a pressure of from about atmospheric to about 500 pounds per square inch, and at a Iliquid hourly space velocity of from about 0.1 to about to produce hydrogen and benzene, removing said benzene as the second product from the process, and recycling at least a portion of said hydrogen to hydroisomerization Zone as the sole source of makeup hydrogen therefor.

9. A combination hydroisomerization and dehydrogenation process for the simultaneous production of dimethylbutanes and benzene, said process self-sufficient in hydrogen requirement, which comprises passing to a first fractionation zone an isomerizable hexane hydrocarbon fraction in combination with liquid phase hydroisomerization zone effluent produced as hereinafter described, Ifractionating said hydrocarbons to produce a substan- .tially cyclohextane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising cyclohexane, passing sa-id cyclohexane bottoms fraction to a dehydrogenation zone hereinafter described, passing said substantially cyclohexane-free overhead hexane fraction vfrom said iirst fractionation zone to a second fractionation zone as feed therefor, fractonating said hydrocarbons to produce an overhead hydrocarbon fraction containing 2,2- and 2,3-dimethy1- butanes and to produce a bottoms hydrocarbon fraction containing methylpentanes, normal hexane, and methylcyclopentane, removing said overhead hydrocarbon fraction containing 2,2- and 2,3- dimethylbutanes as one product from the process, passing said last mentioned bot- 'toms hydrocarbon fraction containing methylpentanes,

normal hexane, `and methylcyclopentane along with hydrogen -at least some of which is produced by dehydrogenation `as hereinafter described to a hydroisomerization zone maintained at a temperature of from about 300 F. to about 500 F. and at a pressure of from about 100 to about 1000 pounds per square inch wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a liquid hourly space velocity of from about 0.1 to about in the presence of a hydroisomerization catalyst comprising platinum deposited on alumina impregnated with aluminum chloride to an equilibrium mixture of hexane hydrocarbons including 2,2- and 2,3-dimethylbutanes, methylpentanes, normal hexane, methylcyclopentane, and cyclohexaue, recycling the hydroisomerization zone eiuent to the iirst mentioned fractionation zone as aforesaid to recover cyclohexane therefrom and to allow recovery therefrom of 2,2- and 2,3-dimethy-lbutanes produced in the process in said second fractionation zone as aforesaid and to separate methylpentanes, normal hexane, and methylcyclopentane as :aforesaid for reuse and internal recycle in said process, dehydrogenating said cyclohexane from the bottoms of said iirst fractionation zone in a dehydrogenation zone in the presence of a chromia-alumina dehydrogenation catalyst at a ternperature of from -about 500 F. to about 1000 F., a pressure of from about atmospheric to about 500Y pounds per Square inch, and at :a liquid hourly 'space velocity of from about 0.1 to about 100 to produce hydrogen and benzene, removing said benzene as the second product from the process, and recycling at least a portion of said hydrogen to the hydroisomenization zone as the sole source of makeup hydrogen therefor. l

t10. A combination hydroisomerization and dehydrogenation process for the simultaneous production of dimethylbutanes and benzene, said process self-suiicient in hydrogen requirement, which comprises passing to a rst fractionation zone an .isomerizable hexane hydrocarbon Afraction in combination with liquid phase hydroisomerization zone eiluent produced as hereinafter described, fractionating said hydrocarbons to produce a substantially cyclohexane-free overhead hydrocarbon fraction and to produce a substantially pure cyclics hydrocarbon bottoms fraction comprising cyclohexane, passing said cyclohexane bottoms fraction to a dehydrogenation zone hereinafter described, passing said substantially cyclohexane-free overhead hexane fraction from said rst fractionation zone to a second fractionation zone as feed therefor, fractionating said hydrocarbons to produce an overhead hydrocarbon fraction containing 2,2- -and 2,3-dimethylbutanes and to produce a bottoms hydrocarbon fraction containing methylpentanes, nor-mal hexane, and methylcyclopentane, removing said overhead hydrocarbon fnactionfcontaining 2,2- and 2,3-dimethylbutanes as one' product from the process,`passing said last mentioned bottoms hydrocarbon fraction containing methylpentanes, normal hexane, kand methylcyclopentane along with hydrogen at least some of which is Vproduced by dehydrogenation as hereinafter described to a hydroisomerization zone maintained at a temperature of from about'300 F. to about 500 F. and at a pressure of from about 100 to about 1000 pounds per square inch wherein methylpentanes, normal hexane, and methylcyclopentane are isomerized at a liquid hourly space velocity of from about 0.1 to about l0 in the presence of a hydroisomerization catalyst comprising platinum deposited on alumina impregnated with aluminum chloride -to an equilibrium mixture of hexane hydrocarbons including 2,2- and 2,3-dimethylbutanes, methylpentanes, normal hexane, methylcyclopentane, and cyclohexane,` recycling the hydroisomerization zone effluent to the first mentioned fraction zone as aforesaid `to recover cyclohexane therefrom and to allow recovery therefrom of 2,2- and 2,3-dimethylbutanes produced in the process -in said second fractionation zone as aforesaid and to separate methylpentanes, normal hexane, and methylcyclopentane as aforesaid for reuse and internal recycle in said process, dehydrogenating said cyclohexane from the bottoms of said iirst `fractionation zone in a dehydrogenation zone in the presence of a molybdena-alumina dehydrogenation catalyst at a temperature of from about-500 F. to about 1000 F., a pressure of from about atmospheric to Vabout 500 pounds per square inch, and at a liquid hourly space velocity of from about 0.1 to about to produce hydrogen and benzene, removing said benzene as the second product from the process, and recycling at least a portion of said hydrogen to the hydroisomezation `zone a's the sole source of makeup hydrogen therefor.

References Cited in the tile of this patent UNITED STATES PATENTS 2,372,711 Cornforth Apr. 3, 1945 2,395,022 Sutton et al. Feb. 19, 1946 2,396,331 Marschner i Mar. 12, 1946 2,425,074 Waugh Aug. 5, 1947 2,766,302 Elkins Oct. 9, 1956 

1. A COMBINATION HYDROISOMERIZATION AND DEHYDROGENATION PROCESS FOR THE SIMULTANEOUS PRODUCTION OF DIMETHYLBUTANES AND BENZENE, SAID PROCESS SELF-SUFFICIENT IN HYDROGEN REQUIREMENT, WHICH COMPRISES PASSING TO A FIRST FRACTIONATION ZONE AN ISOMERIZABLE HEXANE HYDROCARBON FRACTION IN COMBINATION WITH LIQUID PHASE HYDROISOMERIZATION ZONE EFFLUENT PRODUCED AS HEREINAFTER DESCRIBED, FRACTIONATING SAID HYDROCARBONS TO PRODUCE A SUBSTANTIALLY CYCLOHEXANE-FREE OVERHEAD HYDROCARBON FRACTION AND TO PRODUCE A SUBSTANTIALLY PURE CYCLIS HYDROCARBON BOTTOMS FRACTION COMPRISING CYCLOHEXANE, PASSING SAID CYCLOHEXANE BOTTOMS FRACTION TO A DEHYDROGENATION ZONE HEREINAFTER DESCRIBED, PASSING SAID SUBSTANTIALLY CYCLOHEXANE-FREE OVERHEAD HEXANE FRACTION FROM SAID FIRST FRACTIONATION ZONE TO A SECOND FRACTIONATION ZONE AS FEED THEREFOR, FRACTIONATING SAID HYDROCARBONS TO PRODUCE AN OVERHEAD HYDROCARBON FRACTION CONTAINING 2,2- AND 2,3DIMETHYLBUTANES AND TO PRODUCE A BOTTOMS HYDROCARBON FRACTION CONTAINING METHYLPENTANES, NORMAL HEXANE, AND METHYLCYCLOPENTANE, REMOVING SAID OVERHEAD HYDROCARBON FRACTION CONTAINING 2,2- AND 2,3-DIMETHYLBUTANES AS ONE PRODUCT FROM THE PROCESS, PASSING SAID LAST MENTIONED BOTTOMS HYDROCARBON FRACTION CONTAINING METHYLPENTANES, NORMAL HEXANE, AND METHYLCYCLOPENTANE ALONG WITH HYDROGEN AT LEAST SOME OF WHICH IS PRODUCED BY DEHYDROGENATION AS HEREINAFTER DESCRIBED TO A HYDROISOMERIZATION ZONE MAINTAINED AT A TEMPERATURE OF FROM ABOUT 300* F. TO ABOUT 500*F. AND AT A PRESSURE OF FROM ABOUT 300*F. ABOUT 1000 POUNDS PER SQUARE INCH WHEREIN METHYLPENTANES, NORMAL HEXANE, AND METHYLCYCLOPENTANE ARE ISOMERIZED AT A LIQUID HOURLY SPACE VELOCITY OF FROM ABOUT 0.1 TO ABOUT 10 IN THE PRESENCE OF A HYDROISOMERIZATION CATALYST COMPRISING A HYDROGENATION COMPONENT DEPOSITED ON AN ACID-ACTING SUPPORT TO AN EQUILIBRIUM MIXTURE OF HEXANE HYDROCARBONS INCLUDING 2,2- AND 2,3-DIMETHYLBUTANES, METHYLPENTANCES, NORMAL HEXANE, METHYLCYCLOPENTANE, AND CYCLOHEXANE, RECYCLING THE HYDROISOMERIZATION ZONE EFFLUENT TO THE FIRST MENTIONED FRACTIONATION ZONE AS AFORESAID TO RECOVER CYCLOHEXANE THEREFROM AND TO ALLOW RECOVERY THEREFROM OF 2,2- AND 2,3-DIMETHYLBUTANES PRODUCED IN THE PROCESS IN SAID SECOND FRACTIONATION ZONE AS AFORESAID AND TO SEPARATE METHYLPENTANES, NORMAL HEXANE, AND METHYLCYCLOPENTANE AS AFORESAID FOR REUSE AND INTERNAL RECYCLE IN SAID PROCESS, DEHYDROGENATING SAID CYCLOHEXABE FROM THE BOTTOM OF SAID FIRST FRACTIONATION ZONE IN A DEHYDROGENATION ZONE IN THE PRESENCE OF A DEHYDROGENATION CATALYST AT DEHYDROGENATION CONDITIONS TO PRODUCE HYDROGEN AND BENZENE, REMOVING SAID BENZENE AS THE SECOND PRODUCT FROM THE PROCESS, AND RECYCLING AT LEAST A PORTION OF SAID HYDROGEN TO THE HYDROISOMERIZATION ZONE AS THE SOLE SOURCE OF MAKEUP HYDROGEN THEREFOR. 